Insights into the structural dynamics of the Hsp110-Hsp70 interaction reveal the mechanism for nucleotide exchange activity.
Hsp110 proteins are relatives of canonical Hsp70 chaperones and are expressed abundantly in the eukaryotic cytosol. Recently, it has become clear that Hsp110 proteins are essential nucleotide exchange factors (NEFs) for Hsp70 chaperones. Here, we report the architecture of the complex between the yeast Hsp110, Sse1, and its cognate Hsp70 partner, Ssa1, as revealed by hydrogen-deuterium exchange analysis and site-specific cross-linking. The two nucleotide-binding domains (NBDs) of Sse1 and Ssa1 are positioned to face each other and form extensive contacts between opposite lobes of their NBDs. A second contact with the periphery of the Ssa1 NBD lobe II is likely mediated via the protruding C-terminal alpha-helical subdomain of Sse1. To address the mechanism of catalyzed nucleotide exchange, we have compared the hydrogen exchange characteristics of the Ssa1 NBD in complex with either Sse1 or the yeast homologs of the NEFs HspBP1 and Bag-1. We find that Sse1 exploits a Bag-1-like mechanism to catalyze nucleotide release, which involves opening of the Ssa1 NBD by tilting lobe II. Thus, Hsp110 proteins use a unique binding mode to catalyze nucleotide release from Hsp70s by a functionally convergent mechanism.
Andréasson
Claes
C
Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, D-69120 Heidelberg.
Fiaux
Jocelyne
J
Rampelt
Heike
H
Druffel-Augustin
Silke
S
Bukau
Bernd
B
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D004268:DNA-Binding Proteins; D041961:Deuterium Exchange Measurement; D050957:HSP110 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D006360:Heat-Shock Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D018832:Molecular Chaperones; D009711:Nucleotides / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors
C091732:BCL2-associated athanogene 1 protein; D004268:DNA-Binding Proteins; D050957:HSP110 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C086039:MGE1 protein, S cerevisiae; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D018832:Molecular Chaperones; D009711:Nucleotides; C494656:SSE1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000251:Adenosine Triphosphatases; C095973:SSA1 protein, S cerevisiae